1. Field of the Invention
The present invention relates to a communication system and a communication apparatus capable of communicating with a communication apparatus.
2. Description of the Related Art
Conventionally, a CAN (controller area network) communication scheme has been known as a communication scheme between electronic control units such as an ECU (engine electronic control unit) and a motor ECU. According to the CAN communication scheme, various commands or control signals are transmitted between the electronic control units via a communication line called a CAN bus. The CAN communication scheme has widely been used as a communication scheme which is low in cost and is high in the degree of freedom.
In the CAN communication scheme, a master-slave relation is not determined, and instead a so-called multi-master system in which each electronic control unit transmits data at any communication timing has been employed.
Further, as one of communication schemes, there is a known single master system in which communication apparatuses communicate with each other using a master-slave relation. According to the single master system, one of electronic control units in a network serves as a master node and manages a communication schedule, and another electronic control unit (slave node) transmits data in response to a request from the master node.
For example, in a technique disclosed in Japanese Patent Application Laid-Open No. 2004-362067, a master node initially transmits transmission destination slave node information when the master node transmits data to a specific slave node. When it is determined that the destination node information is information destined for the own apparatus with reference to the transmission destination slave node information, each slave node executes a predetermined calculating process based on subsequently transmitted data and transmits the calculation result to the master node.
In the technique disclosed in Japanese Patent Application Laid-Open No. 2004-362067, however, there is some room for further improvement in efficiency of data communication. In the technique disclosed in Japanese Patent Application Laid-Open No. 2004-362067, for example, the transmission destination slave node information is transmitted separate from calculation processing data. Therefore, the amount of data increases by the amount of the transmitted transmission destination slave node information, and therefore the efficiency of data communication is lowered.
When the efficiency of the data communication is lowered, the transmission and reception of data may not be completed within a control period particularly when the data is repeatedly transmitted and received at a predetermined control period between the master and slave nodes.
One aspect of an embodiment is aimed to provide a communication system and communication apparatus that can improve the efficiency of the data communication.